Systems, methods, and physical computer storage media to optimize data placement in multi-tiered storage systems

ABSTRACT

For optimizing data placement in a multi-tiered storage system, system configuration data and system performance data is collected. A plurality of data movement plans are generated, based in part on the system configuration data and the system performance data. A conflict between the plurality of data movement plans are arbitrated to form an execution plan. The data movement plans are performed according to the execution plan.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.13/117,236, filed on May 27, 2011.

FIELD OF THE INVENTION

The present invention relates in general to storage systems, and inparticular to controlling multi-tiered storage systems.

DESCRIPTION OF THE RELATED ART

Multi-tiered storage systems typically include multiple logical andphysical storage devices. These storage devices are divided intomultiple levels, wherein each level is assigned a priority. Data isstored in particular ones of the storage devices, based on the expecteddemand for a particular set of the data and a desired level ofperformance from the storage devices.

In an example, a multi-tiered storage system may be a three-tier system.In such case, a plurality of storage devices having very highperformance capabilities (e.g., for frequent data access and minimalaccess delay) is employed in a highest level of the tiered storagesystem. This tier of the tiered storage system is sometimes referred toas the “online” tier or T0 and typically consists of storage deviceswhich are the most expensive to manufacture and to purchase. A middletier of the tiered storage system, sometimes referred to as the“nearline” tier or T1, has storage devices having a lower performancecapability than T0 but that perform sufficiently to handle regularlyaccessed data or data capable of tolerating larger access delays due tolower performance measures of the storage devices. There may be multiplemiddle tiers in a tiered storage system based on the complexity of thetiered storage system and the differing performance capabilities of thestorage devices employed. A bottom tier of the tiered storage system,sometimes referred to as the “offline” tier, may be comprised ofrelatively low performance storage devices. This tier archives or storesdata that is infrequently accessed and thus, the access delay associatedwith these storage devices is not of a concern.

SUMMARY OF THE INVENTION

Although the aforementioned tiered storage systems operate adequatelywhen storing data, they may be improved. In particular, in some casesthe system may run several processes concurrently that may seek tooptimize data re-allocation of the same data. As a result, the processesmay seek to move the same data from an original location to differentlocations for use. In such case, conflicts may arise as to which processshould access the data. Consequently, a higher overhead and lowerefficiency for data placement optimization may result.

Currently, some systems allow all processes to run despite therequirement of using the same data. In such cases, the systems may haverelatively low efficiency and increased cost due to the data being movedrelatively frequently. Other systems include multiple algorithms tomediate the conflicts. However, the multiple algorithms may notcomplement each other and may cause added conflict within the system.Moreover, adding or removing an algorithm to the existing algorithms mayrequire a redesign of the entire system.

A system, method, and a physical computer storage medium are nowprovided for controlling a multi-tiered storage system to optimize dataplacement for a multi-tiered storage system. In an embodiment, by way ofexample only, the system includes a data collector, a plurality of dataplacement optimizers, a data placement arbitrator, and a data mover. Thedata collector is configured to collect system configuration data andsystem performance data. The plurality of data placement optimizers areeach configured to analyze the system configuration data and the systemperformance data for developing a corresponding data movement plan. Thedata placement arbitrator is configured to arbitrate conflicts betweenat least two data movement plans of generated by the plurality of dataplacement optimizers to form an execution plan. The data mover isconfigured to perform the data movement plans according to the executionplan.

In another embodiment, by way of example only, the method includescollecting system configuration data and system performance data,generating a plurality of data movement plans, based in part on thesystem configuration data and the system performance data, arbitrating aconflict between the plurality of data movement plans to form anexecution plan, and performing the data movement plans according to theexecution plan.

In still another embodiment, by way of example only, the physicalcomputer storage medium includes computer code for collecting systemconfiguration data and system performance data, computer code forgenerating a plurality of data movement plans, based in part on thesystem configuration data and the system performance data, computer codefor arbitrating a conflict between the plurality of data movement plansto form an execution plan, and computer code for performing the datamovement plans according to the execution plan.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the invention will be readilyunderstood, a more particular description of the invention brieflydescribed above will be rendered by reference to specific embodimentsthat are illustrated in the appended drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered to be limiting of its scope, the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings, in which:

FIG. 1 is an example block diagram of a storage device in which aspectsof the illustrative embodiments may be implemented;

FIG. 2 is an example block diagram of a data processing device in whichaspects of the illustrative embodiments may be implemented;

FIG. 3 is a diagram of a framework for use with a multi-tiered storagesystem, according to an embodiment; and

FIG. 4 is a flow diagram of a method of controlling a multi-tieredstorage system, according to an embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

The illustrated embodiments below provide a system for controlling amulti-tiered storage system to optimize data placement for amulti-tiered storage system. Generally, the system includes a datacollector, a plurality of data placement optimizers, a data placementarbitrator, and a data mover. The data collector is configured tocollect system configuration data and system performance data. Theplurality of data placement optimizers are each configured to analyzethe system configuration data and the system performance data fordeveloping a corresponding data movement plan. The data placementarbitrator is configured to arbitrate conflicts between at least twodata movement plans of generated by the plurality of data placementoptimizers to form an execution plan. The data mover is configured toperform the data movement plans according to the execution plan.

With reference now to the figures, example diagrams of data processingenvironments are provided in which illustrative embodiments of thepresent invention may be implemented. It should be appreciated that thefigures are only examples and are not intended to assert or imply anylimitation with regard to the environments in which aspects orembodiments of the present invention may be implemented. Manymodifications to the depicted environments may be made without departingfrom the spirit and scope of the present invention.

With reference now to the figures, FIG. 1 is an example block diagram ofa storage device 50 in which aspects of the illustrative embodiments maybe implemented.

In one embodiment, the storage device 50 includes a storage controller100, one or more switches 102, and storage media 104 such as hard-diskdrives or solid-state drives. The storage controller 100 enables one ormore hosts 52 (e.g., open system and/or mainframe servers) or storagedevices 50 to access data in the storage media 104.

In selected embodiments, the storage controller 100 includes one or moreservers 106. Although two servers 106 are shown, fewer or more can beincluded in other embodiments. The storage controller 100 may alsoinclude host adapters 120 to connect to host devices 52 and otherstorage devices 50. The storage controller 100 may also include deviceadapters 110 to connect to the storage media 104. Multiple servers 106a, 106 b may provide redundancy to ensure that data is always availableto connected hosts. Thus, when one server 106 a fails, the other server106 b may pick up the I/O load of the failed server 106 a to ensure thatI/O is able to continue between the hosts 52 and the storage devices 50.One example of a storage device 50 having an architecture similar tothat illustrated in FIG. 1 is the IBM DS8000™ enterprise storage system(trademark registered to International Business Machines, Inc. ofArmonk, N.Y.).

Nevertheless, embodiments of the invention are not limited to beingimplemented with an IBM DS8000™ enterprise storage system, but may beimplemented in any comparable or analogous storage device 40, regardlessof the manufacturer, product name, or components or component namesassociated with the system. Any storage device 50 that could benefitfrom or be used to implement one or more embodiments of the invention isdeemed to fall within the scope of the invention. Thus, the IBM DS8000™is presented only by way of example.

In selected embodiments, each server 106 may include one or moreprocessors 112 (e.g., n-way symmetric multiprocessors) and memory 114.The memory 114 may include volatile memory (e.g., RAM) as well asnon-volatile memory (e.g., ROM, EPROM, EEPROM, hard disks, flash memory,etc.). The memory 114 may store software modules that run on theprocessor(s) 112 and are used to access data in the storage media 104.The servers 106 may host at least one instance of these softwaremodules, which collectively may also be referred to as a “server,”albeit in software form. These software modules may manage all read andwrite requests to logical volumes in the storage media 104

With reference now to FIG. 2, a block diagram of an example dataprocessing system is shown in which aspects of the illustrativeembodiments may be implemented. Data processing system 200 is an exampleof a computer, such as host 52 in FIG. 1, in which computer usable codeor instructions implementing the processes for illustrative embodimentsof the present invention may be located.

In the depicted example, data processing system 200 employs a hubarchitecture including north bridge and memory controller hub (NB/MCH)202 and south bridge and input/output (I/O) controller hub (SB/ICH) 204.Processing unit 206, main memory 208, and graphics processor 210 areconnected to NB/MCH 202. Graphics processor 210 may be connected toNB/MCH 202 through an accelerated graphics port (AGP).

In the depicted example, local area network (LAN) adapter 212 connectsto SB/ICH 204. Audio adapter 216, keyboard and mouse adapter 220, modem222, read only memory (ROM) 224, hard disk drive (HDD) 226, CD-ROM drive230, universal serial bus (USB) ports and other communication ports 232,and PCI/PCIe devices 234 connect to SB/ICH 204 through bus 238 and bus240. PCI/PCIe devices may include, for example, Ethernet adapters,add-in cards, and PC cards for notebook computers. PCI uses a card buscontroller, while PCIe does not. ROM 224 may be, for example, a flashbasic input/output system (BIOS).

HDD 226 and CD-ROM drive 230 connect to SB/ICH 204 through bus 240. HDD226 and CD-ROM drive 230 may use, for example, an integrated driveelectronics (IDE) or serial advanced technology attachment (SATA)interface. Super I/O (SIO) device 236 may be connected to SB/ICH 204.

An operating system runs on processing unit 206. The operating systemcoordinates and provides control of various components within the dataprocessing system 200 in FIG. 2. As a client, the operating system maybe a commercially available operating system such as Microsoft® Windows®XP (Microsoft and Windows are trademarks of Microsoft Corporation in theUnited States, other countries, or both). An object-oriented programmingsystem, such as the Java™ programming system, may run in conjunctionwith the operating system and provides calls to the operating systemfrom Java™ programs or applications executing on data processing system200 (Java is a trademark of Sun Microsystems, Inc. in the United States,other countries, or both).

As a server, data processing system 200 may be, for example, an IBM®eServer™ System p® computer system, running the Advanced InteractiveExecutive (AIX®) operating system or the LINUX® operating system(eServer, System p, and AIX are trademarks of International BusinessMachines Corporation in the United States, other countries, or bothwhile LINUX is a trademark of Linus Torvalds in the United States, othercountries, or both). Data processing system 200 may be a symmetricmultiprocessor (SMP) system including a plurality of processors inprocessing unit 206. Alternatively, a single processor system may beemployed. Moreover, in one illustrative embodiment, the data processingsystem 200 may be comprised of one or more System p servers with anetwork of host adapters to communicate over the network 102 in FIG. 1,and a network of RAID adapters to communicate to a plethora of storagedevices.

Computer code for the operating system, the object-oriented programmingsystem, and applications or programs are located on storage devices,such as HDD 226, and may be loaded into main memory 208 for execution byprocessing unit 206. The processes for illustrative embodiments of thepresent invention may be performed by processing unit 206 using computerusable program code, which may be located in a memory such as, forexample, main memory 208, ROM 224, or in one or more peripheral devices226 and 230, for example.

A bus system, such as bus 238 or bus 240 as shown in FIG. 2, may becomprised of one or more buses. Of course, the bus system may beimplemented using any type of communication fabric or architecture thatprovides for a transfer of data between different components or devicesattached to the fabric or architecture. A communication unit, such asmodem 222 or network adapter 212 of FIG. 2, may include one or moredevices used to transmit and receive data. A memory may be, for example,main memory 208, ROM 224, or a cache such as found in NB/MCH 202 in FIG.2.

Those of ordinary skill in the art will appreciate that the hardware inFIGS. 1-2 may vary depending on the implementation. Other internalhardware or peripheral devices, such as flash memory, equivalentnon-volatile memory, or optical disk drives and the like, may be used inaddition to or in place of the hardware depicted in FIGS. 1-2. Also, theprocesses of the illustrative embodiments may be applied to amultiprocessor data processing system, other than the SMP systemmentioned previously, without departing from the spirit and scope of thepresent invention.

Moreover, the data processing system 200 may take the form of any of anumber of different data processing systems including client computingdevices, server computing devices, a tablet computer, laptop computer,telephone or other communication device, a personal digital assistant(PDA), or the like. In some illustrative examples, data processingsystem 200 may be a portable computing device which is configured withflash memory to provide non-volatile memory for storing operating systemfiles and/or user-generated data, for example. Essentially, dataprocessing system 200 may be any known or later developed dataprocessing system without architectural limitation.

With regard to the illustrative embodiments, one or more of the dataprocessing systems and/or storage systems may include a tiered storagesystem upon which the mechanisms of the illustrative embodiments may beimplemented. The illustrative embodiments operate to optimize movementof data within a tiered storage system so as to make efficient use ofthe varying performance characteristics of the various tiers of storagedevices within the tiered storage system. In another embodiment, aseparate server, such as a typical x86 server can be employed, where theserver communicates with a tiered storage system through a network.

During operation of a tiered storage system, different processes runningon the system may attempt to reallocate the same data to differentlocations. In this regard, the system is configured to include aframework that operates by arbitrating conflicts between two or moredata migration plans in order to reduce unnecessary data movement. FIG.3 is a diagram of a framework 300 for use with a multi-tiered storagesystem (e.g., storage device 50) according to an embodiment. Theframework 300 of the multi-tiered storage system includes a datacollector 302, a plurality of data placement optimizers 303, 305, 307,309, a data placement arbitrator 306, and a data mover 308.

The data collector 302 collects raw data relating to systemconfiguration and system performance. The data collector 302 may resideon one or more servers (e.g., servers 106 a, 106 b) such as a serverincluding a storage controller (e.g., storage controllers 10100). In anembodiment, the system configuration and performance data are stored ona storage controller. The data collector 302 also can reside in thestorage controller. Types of data collected relating to the systemconfiguration include, but are not limited to data related to physicaldevices configurations and corresponding performance characteristics,changes in configuration changes, such as new device add-ins or removalof devices, changes in states of the system, such as system failover,warmstart or user-changed settings. System performance data include, butare not limited to data related to fine-grained performance for eachstorage data set which can be moved atomically, data for detectingpossible storage device performance overheating and data for settingcorresponding flags to notice the data placement optimizers, and datafor obtaining performance feedback after the data is moved to its newlocation, and to refresh to corresponding data placement optimizers.

The data placement optimizers 303, 305, 307, 309 are configured toanalyze the raw data collected by the data collector 302 and to learnfrom the system configuration data and the system performance data togenerate a plurality of data migration plans 310. One or more of thedata placement optimizers 303, 305, 307, 309 reside on one or moreclients (e.g., hosts 52). According to an embodiment, each dataplacement optimizer 303, 305, 307, 309 includes a learning module 311,313, 315, 317 and a generating plan module 319, 321, 323, 325. As aresult, each data placement optimizer 303, 305, 307, 309 is configuredto independently learn and generate a data migration plan. Although fourare shown in FIG. 3, there is no limit to the number of data placementoptimizers 303, 305, 307, 309 that are included in the framework andthus, no limit to the number of data placement plans that can begenerated.

As part of learning, one or more of the data placement optimizers 303,305, 307, 309 can detect frequently accessed data (“hot data”) on alower storage tier, and to generate a plan to move the hot data to ahigher storage tier (such as an upper storage tier) to improve storageperformance. In another embodiment, one or more of the data placementoptimizers 303, 305, 307, 309 can learn to detect rarely accessed data(“cold data”) on the upper storage tier, and to generate a plan to movethe data to a lower storage tier to improve the storage total cost ofownership and power usage. In another example, one or more of the dataplacement optimizers 303, 305, 307, 309 learns to detect hotspot deviceswithin a single tier, and formulates a plan to spread the hotspot toother devices within the tier to improve the storage device utilization.

The data placement optimizers 303, 305, 307, 309 can be configured tolearn to detect storage devices within a tier that are overheating, andto generate plans that demote data in the overheated storage device to alower tier to recover storage performance. In another embodiment, one ormore of the data placement optimizers 303, 305, 307, 309 can beconfigured to learn to interpret a request to move data from a user orfrom one or more applications to thereby form a movement plan to movethe data to specified location for a particular purpose.

The data placement arbitrator 306 is configured to arbitrate conflictsbetween at least two data migration plans of the plurality of datamigration plans to form an execution plan. Specifically, the dataplacement arbitrator 306 includes a plurality of in-cycle conflictresolution modules 312 and a plurality of out-cycle conflict resolutionmodules 314 and reside on one or more clients (e.g., hosts 52). Theplurality of data migration plans 310 generated by the data placementoptimizer 306 are submitted to the in-cycle conflict resolution modules312. The in-cycle conflict resolution modules 312 operate via “first-in,first-out” and resolve conflicts between the data migration plans bydetermining an optimal resolution before submitting the data migrationplans to execution. In particular, the in-cycle conflict resolutionmodules 312 include a defined priority tree for all the data placementoptimizers 303, 305, 307, 309, so that when the data migration plans 310presented by multiple data placement optimizers 303, 305, 307, 309 tryto move the same data, only the plan 310 from the highest priority dataplacement optimizer 306 can be submitted for execution.

For example, a first in-cycle conflict resolution module 312 receivesthe plurality of data migration plans 310 and may identify two of thedata migration plans 310 that are slated to access the same data. Then,a determination is made as to whether a first data migration plan has ahigher priority than a second data migration plan according to thepriority tree. In some cases, the priority tree prioritizes a datamigration plan from a data placement optimizer because movement wouldprovide improved system efficiency, or would improve overall storageperformance, or comply with a customer application request or recoverthe system from an occurring overheating condition, and the like. In anembodiment, if the first data migration plan has a higher priority, thenthat plan is moved forward to another in-cycle conflict resolutionmodule 312 and the second data migration plan is removed from the dataplacement arbitrator 306 or placed on hold. The first data migrationplan is then submitted to the subsequent in-cycle conflict resolutionmodule 312 (e.g., a second, a third, and so on) and a determination ismade as to whether the first data migration plan has a higher prioritymore than a third data migration plan or a fourth data migration plan,and so on. In some cases, the first data migration plan may not havehigher priority and may be removed or placed behind another datamigration plan, while the higher priority plan may move forward. In thisway, all of the data migration plans are reviewed and either placed inan execution plan or removed.

In another embodiment, the data placement arbitrator 306 is configuredto select data migration plans from the data placement optimizers 303,305, 307, 309, based on a predetermined ratio between the data placementoptimizers 303, 305, 307, 309. In some cases, the predetermined ratiocan be adjusted automatically to satisfy a given desired output byreferring to the previously selected data migration plans. In stillanother embodiment, the data placement arbitrator 306 can be configuredto detect a configuration change and can abort a data migration planthat is no longer valid in light of the configuration change.

After the data migration plans have been considered by the in-cycleconflict resolution modules 312, the execution plan is submitted to theout-cycle conflict resolution modules 314. The out-cycle conflictresolution modules 314 can each include a lease time mechanism thatprevents migration of data being used by a particular data migrationplan from being migrated to another location by a different datamigration plan having an equal or lower priority so that the executionplan run for a defined window of time. For example, the defined windowof time may be in a range of about 60 minutes to about 7 days. Inanother embodiment, the defined window of time may be in a range ofabout 24 hours and 7 days hours. In other embodiments, the time periodmay be shorter or longer. In addition to the lease time mechanism, theout-cycle conflict resolution modules 312 include a defined prioritytree for all the data placement optimizers 303, 305, 307, 309, so thatwhen an attempt is made to move data that is being utilized by a runningdata migration plan 310 by another data migration plan 310 having anequal or lower priority, the data is protected from movement. However,if the other data migration plan 310 has a higher priority than therunning data migration plan 310, the higher priority data migration plan310 can overwrite the running data migration plan 310 and the data isreleased to the other data migration plan 310 for use.

The data mover 308 receives the execution plan from the data placementarbitrator 312 and performs the data migration plans according to theexecution plan. In an embodiment, the data mover 308 may reside on oneor more servers (e.g., servers 104, 106) such as a server including astorage controller (e.g., storage controller 100). According to anembodiment, the data mover 308 includes multiple migration queues eachhaving a different priority so that the data migration plans 310 havinghigher priority are entered into a corresponding priority queue andthose with lower priority are entered into a corresponding priorityqueue. In this way, the data migration plans in the higher priorityqueue can be executed faster than those in the lower priority queue. Inan embodiment, the data mover includes a high priority queue 316, amiddle priority queue 318, and a low priority queue 320. One or more ofthe queues 316, 318, 320 can include more sub-queues. In otherembodiments the data mover includes more than three or fewer than threequeues.

To ensure that at least some of the data migration plans in the lowerpriority queue are executed, the data mover 308 is configured to includea rotation method. In an example, the rotation methods can select queuesat different frequency. For example, ten plans in the high priorityqueue 316 may be selected, five plans in the middle priority queue 318may be selected, and one plan in the low priority queue 320 may beselected. In this way, the plans are performed at different frequency,and data migration plans in the high priority queue 316 have a longerperiod of time to run. The data mover 308 is further configured todetect a system resource utilization state so that system performancecan be monitored and data migration occurs optimally without detrimentto the system.

FIG. 4 is a flow diagram of a method 400 of for optimizing dataplacement in a multi-tiered storage system, according to an embodiment.First, system configuration data and system performance data arecollected, step 402. In an embodiment, data collection can be performedby a data collector (e.g., data collector 302).

Next, a plurality of data migration plans are generated, based in parton the system configuration data and the system performance data, step404. Each data migration plan is generated by a data placement optimizer(e.g., data placement optimizer 303, 305, 307, 309). In an embodiment,input/output requests are received by the data optimizers to form theplurality of data migration plans based, in part, on the systemconfiguration data and the system performance data.

Conflicts between the plurality of data migration plans are thenarbitrated to form an execution plan, step 406. In an embodiment, theconflicts are resolved by a data placement arbitrator (e.g., dataplacement arbitrator 306). In an example, a determination is made as towhether a first data migration plan has a higher priority than anotherdata migration plan. According to an embodiment, assuming the first datamigration plan has a priority, execution of data migration plans otherthan the first data migration plans are prevented for a predeterminedlength of time, if those data migration plans have an equal or lowerpriority than the priority of the first data migration plan. Despitepreventing execution during the predetermined length of time, datamigration plans having a higher priority than the priority of the firstdata migration plan are executed over the first data migration plan.

Next, the data migration plans are performed according to the executionplan, step 408. In an embodiment, step 408 is performed by a data mover(e.g., data mover 308). After the data is moved according to theexecution plan, updated system configuration data and updated systemperformance data are generated. The updated data is collected (e.g., bythe data collector) or is provided for consideration as to whether theexecution plan should be updated as well.

By including data placement optimizers and a data placement arbitratoras described above, (e.g., inclusion of the multiple data placementoptimizers and the in-cycle and out-cycle conflict resolution modules),conflicts between plans generated by the different data placementoptimizers are either prevented or resolved to thereby improve theefficiency of data optimization and reduce the unnecessary datamovement. Additionally, because each data placement optimizer worksindependently and is assigned a predetermined priority, redesign of theentire system is avoided when a new data placement optimizer is added orwhen an existing data placement optimizer is disabled. Moreover, theabove-described system provides lower overhead and improves efficiencyfor data placement optimization.

As will be appreciated by one of ordinary skill in the art, aspects ofthe present invention may be embodied as a system, method, or computerprogram product. Accordingly, aspects of the present invention may takethe form of an entirely hardware embodiment, an entirely softwareembodiment (including firmware, resident software, micro-code, etc.) oran embodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module,” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer-readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer-readable medium(s) may beutilized. The computer-readable medium may be a computer-readable signalmedium or a physical computer-readable storage medium. A physicalcomputer readable storage medium may be, for example, but not limitedto, an electronic, magnetic, optical, crystal, polymer, electromagnetic,infrared, or semiconductor system, apparatus, or device, or any suitablecombination of the foregoing. Examples of a physical computer-readablestorage medium include, but are not limited to, an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk,RAM, ROM, an EPROM, a Flash memory, an optical fiber, a CD-ROM, anoptical storage device, a magnetic storage device, or any suitablecombination of the foregoing. In the context of this document, acomputer-readable storage medium may be any tangible medium that cancontain, or store a program or data for use by or in connection with aninstruction execution system, apparatus, or device.

Computer code embodied on a computer-readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wired, optical fiber cable, radio frequency (RF), etc., or any suitablecombination of the foregoing. Computer code for carrying out operationsfor aspects of the present invention may be written in any staticlanguage, such as the “C” programming language or other similarprogramming language. The computer code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, or communication system, including, but notlimited to, a local area network (LAN) or a wide area network (WAN),Converged Network, or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).

Aspects of the present invention are described above with reference toflow diagrams and/or block diagrams of methods, apparatus (systems) andcomputer program products according to embodiments of the invention. Itwill be understood that each block of the flow diagrams and/or blockdiagrams, and combinations of blocks in the flow diagrams and/or blockdiagrams, can be implemented by computer program instructions. Thesecomputer program instructions may be provided to a processor of ageneral purpose computer, special purpose computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions, which execute via the processor of the computer orother programmable data processing apparatus, create means forimplementing the functions/acts specified in the flow diagram and/orblock diagram block or blocks.

These computer program instructions may also be stored in acomputer-readable medium that can direct a computer, other programmabledata processing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer-readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flow diagram and/or blockdiagram block or blocks. The computer program instructions may also beloaded onto a computer, other programmable data processing apparatus, orother devices to cause a series of operational steps to be performed onthe computer, other programmable apparatus or other devices to produce acomputer implemented process such that the instructions which execute onthe computer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flow diagram and/orblock diagram block or blocks.

The flow diagrams and block diagrams in the above figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflow diagrams or block diagrams may represent a module, segment, orportion of code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flow diagrams, andcombinations of blocks in the block diagrams and/or flow diagram, can beimplemented by special purpose hardware-based systems that perform thespecified functions or acts, or combinations of special purpose hardwareand computer instructions.

What is claimed is:
 1. A method of optimizing data placement in amulti-tiered storage system, the method comprising: collecting systemconfiguration data and system performance data; generating a pluralityof data movement plans for execution, based in part on the systemconfiguration data and the system performance data; arbitratingpotential conflicts between the plurality of data movement plans slatedto access the same data in the multi-tiered storage system to form anexecution plan, wherein arbitrating the potential conflicts is performedprior to execution of the data movement plans and all of the datamovement plans generated by the plurality of data placement optimizersare included in the execution plan or removed as a result of thearbitrating; and performing the data movement plans according to theexecution plan, wherein: the arbitrating further includes maintaining aplurality of priority queues, each priority queue having a differentpriority, each data movement plan having a priority and being enteredinto a priority queue having a corresponding priority, and theperforming the data movement plans includes executing the data movementplans in a higher priority queue more frequently than the data movementplans in a lower priority queue.
 2. The method of claim 1, furthercomprising updating the execution plan after receiving a result of theperformance of the data movement plans.
 3. The method of claim 1,further comprising collecting updated system configuration data andupdated system performance data as a result of the step of performing.4. The method of claim 1, further comprising receiving input/outputrequests to form a plurality of data migration plans based, in part, onthe system configuration data and the system performance data.
 5. Themethod of claim 4, further comprising determining whether a first datamigration plan has a higher priority than another data migration plan.6. The method of claim 5, wherein: the first data migration plan has apriority; and the method further comprises preventing execution of datamigration plans other than the first data migration plan for apredetermined length of time, if the data migration plans have an equalor lower priority than the priority of the first data migration plan. 7.The method of claim 6, wherein: during the step of preventing execution,executing data migration plans having a higher priority than thepriority of the first data migration plan to be executed over the firstdata migration plan.